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    <title>Document</title>
    <script>
        // var a = 3;
        // var b = 5;
        // // var c = a;
        // // a = b;
        // // b = c;
        // a = a ^ b; //011 ^ 101 = 110 = 6
        // b = a ^ b; //110 ^ 101 = 011 = 3
        // a = a ^ b; // 110 ^ 011 =101 = 5
        // console.log(a,b)
        
        // var age = 20;
        // var res = age > 30? "步入中年" : "小鲜肉";
        // console.log(res);
        // var res2 = age > 30? "步入中年" :age > 25? "25-30" : "仙女";

        var score = prompt("请输入成绩");
        var res = score>=90? "A" :score>=80? "B" : score>=60? "C" :"D";
        console.log(res); 


    </script>
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